Hi,

It still could be a bad FPR. It does not have to leak from the diaphragm and into the vacuum hose to run rich. The FPR could not be returning enough fuel back to the gas tank.
This can happen if the FPR goes out of adjustment internally, the ball and seat get sticky or the return line gets restricted.
These issues with the FPR are the flip side of what can go wrong with them and are more rare.

If the pressure on the fuel rail can rise in any of the cases, a slightly richer mixture will result. Drivability may even be slightly better, power wise, but the fuel consumption will increase.
You are lucky, I think, that the '93 has a fuel rail Schrader vale that a refrigerant gauge can be put on to check the operating pressure. I added one onto my '86 many many years ago. Maybe before the 93's I don't know?

Check the spark plugs to see if they are running fluffy black with carbon. This will tell you the most.

The FPR is mechanical. The computer has no control over it. The computer can only reduce the pluse width according to the O2 sensor output signal.
This is where the codes come in but they will not tell you much more other than you are running too rich for about four non descript reasons. I like to say it's a shotgun blast at the problem. You are hitting something but looking at how many places!

The next thing to look into is a fail Coolant thermostat. Failing in the open or partial open position. The engine maybe running to cool and this makes the engine run richer. The CEL, most likely, will not throw a particular code for that either.

The next thing is the Engine Coolant Sensor for the computer, not the gauge on the dash. There are two sensors. The one on the left front is the instrument one. The one for the computer is under the third intake runner. It's in a harder place to get too, of course!

There is a specification for the resistance range that it should put out at a certain temperature. The hotter the engine the less resistance.
There is more information available on how to check the resistance on certain pins on the ECU on the right kick panel. It's a lot easier to get to and you can check the wiring while you are under there, from it.
If the sensors terminals get corroded or if worse it gets unplugged the car runs richer, like for in Alaska!

All this will give you plenty to sort through. Pick the one you think is most likely to have changed on you or has been the most neglected, as the case may be. Heck there might be a burned out CELight. Lucky you, if so!
These cars need a little TLC every once in awhile.

Phil